JPH0898901A - Solid golf ball and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a solid golf ball having a soft and good shot feeling and a long flight distance. A solid golf ball having a core and a cover covering the core directly or through an intermediate layer,
Butadiene rubber containing 90% or more of cis structure was used as the base rubber of the core before vulcanization, and the trans structure was 10
-30% and the core hardness according to JIS
With respect to the hardness measured with a C-type hardness meter, each hardness at a 5 mm point interval from the center of the core toward the surface should be within 10% of the hardness of the center of the core. The core is preferably vulcanized by two-stage vulcanization in which the core is heated at 135 to 155 ° C. for 20 to 50 minutes and then at 160 to 180 ° C. for 5 to 20 minutes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid golf ball and a method for producing the same, and more particularly to a solid golf ball having a good shot feeling and a good flight distance and a long flight distance, and a method for producing the solid golf ball. Is.

[0002]

2. Description of the Related Art Golf balls are roughly classified into solid golf balls and thread-wound golf balls. Although the former solid golf ball is often used because of its excellent flight performance, it has a problem that the shot feeling is harder than that of a thread-wound golf ball, and a very hard feel is given especially on a miss shot.

Therefore, recently, studies have been made to make the feel of a solid golf ball closer to that of a thread-wound golf ball. For example, the solid golf ball has a soft core to soften the hardness of the entire ball. It has been proposed to improve the shot feeling.

However, when the core is softened, the resilience performance is reduced and the flight distance is reduced accordingly.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problems associated with solid golf balls as described above, improves the feel at impact of solid golf balls without causing a reduction in the resilience performance, and provides a soft feel at impact. The object of the present invention is to provide a solid golf ball which is excellent in flight distance and has a long flight distance.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies focusing on the transition from the cis structure to the trans structure of the rubber of the core of the solid golf ball and the hardness distribution. A part of the cis structure before vulcanization is transformed so that the trans structure becomes 10 to 30% after vulcanization,
The hardness of the core is the hardness measured by JIS-C type hardness tester,
By setting the hardness of each 5 mm point interval from the center of the core to the surface within a range of 10% with respect to the hardness of the center of the core, the resilience performance is not deteriorated even if the core is softened, and the shot feeling is improved. It was found that a solid golf ball which is soft and good and has a long flight distance can be obtained, and has completed the present invention.

That is, according to the present invention, butadiene rubber containing 90% or more of cis structure is used as the base rubber of the core before vulcanization so that the trans structure becomes 10 to 30% after vulcanization, and the hardness of the core is By flattening the distribution as described above, even if the core is softened, the resilience performance is not deteriorated, the feel at impact is soft and good, and the solid golf ball with a large flight distance is provided. is there.

The rubber composition for forming the core is
It contains rubber, a vulcanizing agent (crosslinking agent), a filler, an organic peroxide and an organic sulfur compound as main components.

The rubber has a cis structure of 9 before vulcanization.
Butadiene rubber containing 0% or more is used as a base rubber, and if desired, natural rubber, isoprene rubber, styrene butadiene rubber, ethylene propylene diene rubber (EPDM) or the like may be blended appropriately. However, it is preferable that the butadiene rubber containing 90% of the cis structure is 80% by weight or more in the total rubber.

Various vulcanizing agents may be used without particular limitation, and examples thereof include metal salts of unsaturated carboxylic acids, particularly unsaturated carboxylic acids having 3 to 8 carbon atoms (eg acrylic acid, methacrylic acid). A monovalent or divalent metal salt (such as an acid) is used, and zinc acrylate and zinc methacrylate are particularly preferable. The compounding amount of this vulcanizing agent is 10
20 to 40 parts by weight is preferable relative to 0 parts by weight, especially 2
5 to 35 parts by weight is preferable. If the blending amount of the vulcanizing agent is less than the above range, the hardness of the ball becomes insufficient, the shot feeling (feeling) becomes heavy and deteriorates, and the durability may decrease. On the other hand, if the blending amount of the vulcanizing agent exceeds the above range, the ball becomes too hard and the shot feeling may be deteriorated. Since the metal salt of unsaturated carboxylic acid does not contain sulfur (sulfur), it may be more appropriate to describe it as a crosslinking agent rather than a vulcanizing agent. Then, it is expressed as a vulcanizing agent according to the practice in the art. Further, in the production of the core, the vulcanization of the rubber composition performed by the above-mentioned vulcanizing agent is not due to the cross-linking bond with sulfur, so it may be more appropriate to express it as cross-linking rather than vulcanization. But not
In this case as well, it is referred to as vulcanization in this specification in accordance with the practice in the art.

As the organic peroxide, for example, dicumyl peroxide, di-t-butyl peroxide, etc. are used, but dicumyl peroxide is particularly preferable. The compounding amount of this organic peroxide is preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of rubber. When the content of the organic peroxide is less than the above range, the hardness of the ball is insufficient, and the shot feeling is heavy and deteriorates. When the content of the organic peroxide is more than the above range, the ball becomes too hard. , The shot feeling may be deteriorated.

As the organic sulfur compound, for example, diphenyl disulfide, dixyl disulfide, ditolyl disulfide and the like are used, but it is particularly preferable to use a mixture of three kinds of the above diphenyl disulfide, dixyl disulfide and ditolyl disulfide. . The mixing ratio at that time is not particularly limited, but when the total weight ratio is 100, diphenyldisulfide: dixyldisulfide: ditolyldisulfide is 5-60: 5-60: 5-60. Range, especially 10
The range of 50:10 to 50:10 to 50 is preferable.

The blending amount of the above organic sulfur compound is
0.5 to 4 parts by weight is preferable with respect to 100 parts by weight of rubber. If the blending amount of the organic sulfur compound is less than the above range, the cis structure is not transferred to the trans structure to a desired degree, and it becomes difficult to achieve a soft shot feeling and a large flight distance, If the blending amount of the organic sulfur compound exceeds the above range, the shot feeling may be too soft and the resilience performance may be deteriorated.

As the filler, for example, zinc oxide, titanium dioxide, barium sulfate and the like are generally used. The filler mainly acts as a weight adjusting agent, and its compounding amount is a cover or a core. It is affected by the specific gravity, size, etc., and is not particularly limited, but usually 10 to 40 parts by weight is preferable with respect to 100 parts by weight of rubber.

In the rubber composition used for the golf ball of the present invention, in addition to the main components such as the above rubber, vulcanizing agent, filler, organic peroxide and organic sulfur compound, if necessary,
Additives such as an anti-aging agent can be appropriately added.

The above rubber composition can be prepared by a conventional method similar to the conventional one. However, the vulcanization at the time of producing a core using the above rubber composition, the first stage is 1
Heat at 35-155 ° C. for 20-50 minutes, the second stage is 1
It is preferable to carry out by two-step vulcanization in which heating is performed at 60 to 180 ° C. for 5 to 20 minutes. By performing vulcanization by such two-step vulcanization, the cis structure of the base rubber is transformed to a trans structure to a desired degree, and the hardness distribution of the core is flattened.

The size of the core varies depending on the thickness of the cover, the presence or absence of the intermediate layer, and the like, and is not particularly limited, but is preferably about 35 to 40 mm.

In the present invention, the cis structure before vulcanization of the butadiene rubber used as the base rubber is required to be 90% or more. The reason is that a core having good resilience performance is required unless it has such a high cis structure. Because you can't get it,
Also, the transformer structure of the base rubber after vulcanization is 10 to 30%.
It is necessary that the transformer structure be 10
If it is less than%, the core becomes hard and the shot feeling becomes poor, and if the transformer structure is more than 30%, the core becomes too soft and the resilience performance deteriorates.

The hardness of the core of the golf ball of the present invention is the hardness measured by a JIS-C type hardness tester. Each hardness at 5 mm point intervals from the center of the core toward the surface is relative to the hardness of the center of the core. The difference within 10%. In this way, each hardness at 5 mm point intervals is 10% of the hardness at the center of the core.
The difference within the range indicates that the core is flatly vulcanized. Due to such flat vulcanization and the presence of the organic sulfur compound, the cis structure of the base rubber is changed to the trans structure. Therefore, even if the core is softened and the core is softened, the resilience performance is not deteriorated, the hit feeling is soft and good, and the solid golf ball having a long flight distance can be obtained. That is, if the hardness of the 5 mm point interval from the center of the core toward the surface is greater than 10% of the hardness of the center of the core, the feel at impact becomes heavy.

The hardness of the center of the core is JIS-
The hardness measured by a C-type hardness meter is preferably 60 to 85, and particularly preferably 65 to 80. When the hardness of the center of the core is lower than the above range, the core is too soft and gives a heavy shot feeling, and when the hardness of the center of the core is higher than the above range,
The impact force at the time of hitting may become too large, and the shot feeling may deteriorate.

Next, the structure of the golf ball of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view schematically showing an example of the golf ball of the present invention. The golf ball shown in FIG. 1 is a two-piece solid golf ball including a core 1 and a cover 2 covering the core 1. As described above, the core 1 is formed by vulcanizing a rubber composition having butadiene rubber containing 90% or more of cis structure as a base rubber before vulcanization, and the trans structure after vulcanization is 10 to 30. %
And has a hardness distribution in which each hardness at a 5 mm point interval from the center of the core to the surface measured with a JIS-C type hardness meter is within 10% of the hardness of the center of the core. is there.

As the cover 2, for example, either a resin-based cover mainly composed of an ionomer resin or a balata-based cover can be applied, and 2a is a dimple, and the dimple 2a is required or The cover 2 is provided in an appropriate number and manner so that desired characteristics can be obtained. In addition, paint or marking is applied to the surface of the golf ball, if necessary.

The golf ball shown in FIG. 1 is a two-piece solid golf ball in which the cover 1 is directly coated on the core 1. However, an intermediate layer is provided between the core 1 and the cover 2, and the cover 2 has the intermediate layer. It may be of a type in which the core 1 is covered with a layer.

The method for coating the cover 2 on the core 1 is as follows.
The method is not particularly limited, and the same method as the conventional method can be used. For example, a resin-based cover composition or balata-based cover composition containing an ionomer resin or the like as a main material is previously molded into a hemispherical shell-shaped half shell, and two cores are used to wrap the core 1 at 130 to 170 ° C. So 1 to 1
Press molding for 5 minutes or apply the cover composition to the core 1
For example, a method of directly injection-molding the core 1 and wrapping the core 1 is adopted. The cover preferably has a thickness of about 1 to 4 mm, and when forming the cover, dimples are formed on the surface of the ball as necessary. Also, after the cover is formed, paint finish or
Markings are also given as needed.

[0025]

EXAMPLES Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to only those examples.

Examples 1 to 3 and Comparative Examples 1 to 5 Rubber compositions for cores were prepared with the compounding compositions shown in Tables 1 and 2. The obtained rubber composition for cores was vulcanized and molded in a mold under the vulcanization conditions shown in Tables 1 and 2 to prepare cores having a diameter of 39.2 mm. Table 1 shows the composition and vulcanization conditions of Examples 1 to 3, and Table 2 shows the composition and vulcanization conditions of Comparative Examples 1 to 5. The blending amounts in Tables 1 and 2 are parts by weight, and the details of the components common to Tables 1 and 2 are shown in Table 1.

[0027]

[Table 1]

* 1: Trade name, butadiene rubber manufactured by Nippon Synthetic Rubber Co., Ltd., cis structure content 94% * 2: Yoshinox 425 (trade name) manufactured by Yoshitomi Pharmaceutical Co., Ltd. * 3: Trade name, Seiko Chemical Industry ( Co., Ltd., a mixture of three kinds of diphenyl disulfide, dixyl disulfide, and ditolyl disulfide, the mixing ratio of which is 14.
It is 5: 36.3: 49.2.

[0029]

[Table 2]

The cis structure content and trans structure content of the rubber before vulcanization [BR01 (trade name), that is, butadiene rubber] and the cis structure content and trans structure content of the rubber after vulcanization were measured, and the results are shown in Tables 3 to 3. It shows in Table 4. These measurements were carried out by a method using a Fourier transform infrared spectroscopic absorption spectrometer in combination with the ATR method and the KBR method.

Further, the hardness, compressive strength and coefficient of restitution of the obtained core were measured. The results are shown in Tables 3 to 4.
The hardness was measured at the center of the core (center), 5 mm away from the center to the surface side (5 mm from the center), 10 mm from the center to the surface side (10 mm from the center), and 15 mm from the center to the surface side. Place (15m from the center
m) and the hardness of the surface of the core (surface) were measured by a JIS-C type hardness meter. The hardness of the inside of the core is obtained by cutting the core at the corresponding position and measuring the hardness of the cut surface, and the indications in parentheses at the end of the measurement position are shown in Tables 3 to 4. It is a simplified display when showing a position.

The compressive strength of the above core is obtained by applying an initial load of 10 to the core.
It was determined by measuring the amount of compressive deformation of the core from the time of applying a kg to the time of applying a final load of 130 kg.
The velocity of the ball when the metal cylinder was collided at a velocity of 45 m / s was measured, and the velocity was calculated by calculating from the velocity of the ball. The index is shown when the core of Example 1 is 100.

[0033]

[Table 3]

[0034]

[Table 4]

Next, the above core was covered with an ionomer resin-based cover to manufacture a two-piece solid golf ball having an outer diameter of 42.7 mm. The cover composition was prepared by mixing 2 parts by weight of titanium dioxide with 100 parts by weight of a mixture of Himilan 1605 (trade name) and Himilan 1706 (trade name) in a weight ratio of 50:50. Dupont Polychemical Co., Ltd.'s sodium ion neutralization type ionomer resin, and Himilan 1706 is Mitsui DuPont Polychemical's zinc ion neutralization type ionomer resin.

With respect to the obtained golf ball, the compression strength and flight distance (carry) were measured, and the shot feeling was evaluated.
The results are shown in Tables 5 to 6.

The compressive strength of the ball is obtained by measuring the amount of compressive deformation of the ball from when the initial load of 10 kg is applied to when the final load of 130 kg is applied, and the flight distance is true. The Wood No. 1 club is attached to the swing robot made by Temper, and the ball is 45 m.
It is obtained by hitting at a head speed of / s and measuring the distance (carry) to the falling point. Then, the shot feeling was evaluated by 10 professionals actually hitting the No. 1 wood club.

[0038]

[Table 5]

[0039]

[Table 6]

Tables 1, 3 and 5 show the composition of cores of Examples 1 to 3, vulcanization conditions, cis structure content before vulcanization, trans structure content after vulcanization, hardness distribution of core, compressive strength, The coefficient of restitution, the compression strength of the obtained golf ball, the flight distance, and the shot feeling are shown. Tables 2, 4, and 6 show those for Comparative Examples 1 to 5, but as shown in Table 5, The golf balls of Examples 1 to 3 had a good shot feeling and a good flight distance.

That is, in the golf balls of Examples 1 to 3, the core rubber contained 90% or more of the cis structure before vulcanization, and after vulcanization, the trans structure increased to fall within the range of 10 to 30%. The hardness distribution of the core is flat, and the hardness at each measurement point is within 10% of the hardness at the center, which softens the feel at impact and maintains a great flight distance without causing a reduction in the resilience performance. It is believed that

On the other hand, the golf ball of Comparative Example 4 had a great flight distance, but the shot feeling was hard and bad, and the defects of the solid golf ball were directly exhibited. In addition, the golf balls of Comparative Examples 1 to 3 and Comparative Example 5 have a slightly improved shot feeling compared to Comparative Example 4 but are not sufficient, and particularly the golf balls of Comparative Examples 2 to 3 and Comparative Example 5 are not satisfactory. Had a shorter flight distance than the golf balls of Examples 1 to 3.

[0043]

As described above, according to the present invention, it is possible to provide a solid golf ball having a soft and good shot feeling and a long flight distance.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an example of a solid golf ball according to the present invention.

[Explanation of symbols]

 1 core 2 cover

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Iwami 41-1 Shimizu, Uozumi-cho, Akashi-shi, Hyogo Sumitomo Rubber Fish Dormitory (72) Inventor Masatoshi Yokota 2-5-5-205 Nishimidoka, Toyonaka-shi, Osaka

Claims (2)

[Claims] 1. A solid golf ball having a core and a cover that covers the core directly or via an intermediate layer, wherein the core has a butadiene rubber containing 90% or more of a cis structure before vulcanization as a base rubber. The rubber composition is vulcanized, the transformer structure after vulcanization is 10 to 30%, and the hardness of the core is the hardness measured by a JIS-C type hardness meter, and the surface from the center of the core The solid golf ball is characterized in that each of the hardnesses at 5 mm point intervals facing each other is within 10% of the hardness at the center of the core. 2. The core is vulcanized at 135 to 155 ° C. for 20 minutes.
Heat for ~ 50 minutes, then 5 ~ 20 at 160 ~ 180 ° C
A two-stage vulcanization method of heating for one minute is performed.
A method for producing the solid golf ball described above.